1. Field of the Invention
This invention relates to a treatment apparatus employing a plurality of washing units for washing semiconductor wafers on a continuous basis.
2. Description of the Related Art
A wafer washing apparatus employed in a semiconductor wafer manufacturing system, for example, is used as a treatment apparatus having a plurality of treatment units for continuously treating objects.
In the washing apparatus, semiconductor wafers are subjected to ammonia treatment, water rinse treatment, hydrofluoric acid treatment, etc., on a continuous basis.
To perform such treatments, a conventional washing apparatus is constructed such that a plurality of treatment vessels for respectively performing the treatments are arranged in a row, and that semiconductor wafers to be treated are transferred to the vessels by means of a transfer device movable along the vessels.
Arranging the vessels in a row inevitably requires a large elongated space, and requires the transfer unit to move a long distance.
Further, to transfer the wafers between adjacent ones of the vessels the conventional washing apparatus is equipped with a plurality of linear transfer units each arranged between adjacent vessels, and driving units for driving the transfer units, respectively. Provision of a plurality of driving units may lower the energy efficiency, and cause dust. The dust may lower the yield of products, in particular, in the case of manufacturing semiconductor wafers. If, on the other hand, a common transfer unit is used in place of a plurality of transfer units, then the throughput will inevitably be lowered.